title: The mitochondrial carrier Rim2 co-imports pyrimidine nucleotides and iron.
abstract: Mitochondrial iron uptake is of key importance both for organelle function and cellular iron homoeostasis. The mitochondrial carrier family members Mrs3 and Mrs4 (homologues of vertebrate mitoferrin) function in organellar iron supply, yet other low efficiency transporters may exist. In Saccharomyces cerevisiae, overexpression of RIM2 (MRS12) encoding a mitochondrial pyrimidine nucleotide transporter can overcome the iron-related phenotypes of strains lacking both MRS3 and MRS4. In the present study we show by in vitro transport studies that Rim2 mediates the transport of iron and other divalent metal ions across the mitochondrial inner membrane in a pyrimidine nucleotide-dependent fashion. Mutations in the proposed substrate-binding site of Rim2 prevent both pyrimidine nucleotide and divalent ion transport. These results document that Rim2 catalyses the co-import of pyrimidine nucleotides and divalent metal ions including ferrous iron. The deletion of RIM2 alone has no significant effect on mitochondrial iron supply, Fe-S protein maturation and haem synthesis. However, RIM2 deletion in mrs3/4Δ cells aggravates their Fe-S protein maturation defect. We conclude that under normal physiological conditions Rim2 does not play a significant role in mitochondrial iron acquisition, yet, in the absence of the main iron transporters Mrs3 and Mrs4, this carrier can supply the mitochondrial matrix with iron in a pyrimidine-nucleotide-dependent fashion.
authors.affiliation: *Max F. Perutz Laboratories, Department of Microbiology, Immunology and Genetics, University of Vienna, Dr. Bohrgasse 9, A-1030 Vienna, Austria.
authors.forename: Elisabeth M
authors.initials: EM
authors.lastname: Froschauer
authors.forename: Nicole
authors.initials: N
authors.lastname: Rietzschel
authors.forename: Melanie R
authors.initials: MR
authors.lastname: Hassler
authors.forename: Markus
authors.initials: M
authors.lastname: Binder
authors.forename: Rudolf J
authors.initials: RJ
authors.lastname: Schweyen
authors.forename: Roland
authors.initials: R
authors.lastname: Lill
authors.forename: Ulrich
authors.initials: U
authors.lastname: Mühlenhoff
authors.forename: Gerlinde
authors.initials: G
authors.lastname: Wiesenberger
mesh_terms: D001665:Binding Sites; D001692:Biological Transport; D027682:Cation Transport Proteins / Q000172:deficiency / Q000235:genetics; D002413:Cations, Divalent; D006418:Heme / Q000096:biosynthesis; D007501:Iron / Q000378:metabolism*; D008928:Mitochondria / Q000235:genetics / Q000378:metabolism*; D051336:Mitochondrial Membranes / Q000378:metabolism*; D024101:Mitochondrial Proteins / Q000172:deficiency / Q000235:genetics; D009154:Mutation; D033704:Nucleotide Transport Proteins / Q000235:genetics / Q000378:metabolism*; D010084:Oxidation-Reduction; D011485:Protein Binding; D011742:Pyrimidine Nucleotides / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D027682:Cation Transport Proteins; D002413:Cations, Divalent; C066985:MRS3 protein, S cerevisiae; C066986:MRS4 protein, S cerevisiae; D024101:Mitochondrial Proteins; D033704:Nucleotide Transport Proteins; D011742:Pyrimidine Nucleotides; C092511:RIM2 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D006418:Heme; D007501:Iron